[XFS] Fix accidental reverting of sync write preallocations.

SGI Modid: xfs-linux:xfs-kern:176195a
Signed-off-by: Nathan Scott <nathans@sgi.com>

fs/xfs/linux-2.6/xfs_aops.c

@@ -993,17 +993,6 @@ linvfs_get_block(
 					create, 0, BMAPI_WRITE);
 }
 
-STATIC int
-linvfs_get_block_sync(
-	struct inode		*inode,
-	sector_t		iblock,
-	struct buffer_head	*bh_result,
-	int			create)
-{
-	return linvfs_get_block_core(inode, iblock, 0, bh_result,
-					create, 0, BMAPI_SYNC|BMAPI_WRITE);
-}
-
 STATIC int
 linvfs_get_blocks_direct(
 	struct inode		*inode,
@@ -1258,13 +1247,7 @@ linvfs_prepare_write(
 	unsigned int		from,
 	unsigned int		to)
 {
-	if (file && (file->f_flags & O_SYNC)) {
-		return block_prepare_write(page, from, to,
-						linvfs_get_block_sync);
-	} else {
-		return block_prepare_write(page, from, to,
-						linvfs_get_block);
-	}
+	return block_prepare_write(page, from, to, linvfs_get_block);
 }
 
 struct address_space_operations linvfs_aops = {

fs/xfs/xfs_iomap.c

@@ -585,8 +585,10 @@ xfs_iomap_write_delay(
 	 * out to the file system's write iosize.  We clean up any extra
 	 * space left over when the file is closed in xfs_inactive().
 	 *
-	 * We don't bother with this for sync writes, because we need
-	 * to minimize the amount we write for good performance.
+	 * For sync writes, we are flushing delayed allocate space to
+	 * try to make additional space available for allocation near
+	 * the filesystem full boundary - preallocation hurts in that
+	 * situation, of course.
 	 */
 	if (!(ioflag & BMAPI_SYNC) && ((offset + count) > ip->i_d.di_size)) {
 		xfs_off_t	aligned_offset;

fs/xfs/xfs_iomap.h

@@ -58,7 +58,7 @@ typedef enum {
 	BMAPI_IGNSTATE = (1 << 4),	/* ignore unwritten state on read */
 	BMAPI_DIRECT = (1 << 5),		/* direct instead of buffered write */
 	BMAPI_MMAP = (1 << 6),		/* allocate for mmap write */
-	BMAPI_SYNC = (1 << 7),		/* sync write */
+	BMAPI_SYNC = (1 << 7),		/* sync write to flush delalloc space */
 	BMAPI_TRYLOCK = (1 << 8),	/* non-blocking request */
 	BMAPI_DEVICE = (1 << 9),	/* we only want to know the device */
 } bmapi_flags_t;